When on-site cleaning of liquid pathways of equipment such as filling equipment that fills beverages, etc. into containers, such as bottles and cans, liquid-treatment equipment for filling solutions, or pipe equipment that connects these pieces of equipment is performed after the end of production or before the start of production, cleaning is performed through the circulation of hot water or single rinsing, and the circulation of chemicals such as acids or caustic solutions.
In recent years, it has become apparent that cleaning effects and the like can be improved when small bubbles (nanobubbles) having a diameter of 1 micrometer (μm) or less are contained in cleaning liquid, and research on the generation of nanobubbles has been performed (Patent Document 1).